Reduced link bandwidth update systems and methods for improved scalability, efficiency, and performance

ABSTRACT

A method, node, and network for reduced link bandwidth updates from a first node and a second node forming a link in a network includes, responsive to establishment or release of one or more connections on the link, flooding an update related thereto from only a master node that is one of the first node and the second node; responsive to a link failure associated with the link, flooding an update related thereto from both the first node and the second node; and, responsive to a change in parameters associated with the link, flooding an update related thereto from both the first node and the second node. The flooding can be part of a control plane associated with the network and/or to a Software Defined Networking (SDN) controller.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to networking systems andmethods. More particularly, the present disclosure relates to reducedlink bandwidth update systems and methods in control planes, SoftwareDefined Networking (SDN), and the like.

BACKGROUND OF THE DISCLOSURE

Networks at various layers are being deployed with control planes,Software Defined Networking (SDN), Network Functions Virtualization(NFV), and the like. Control planes provide automatic allocation ofnetwork resources in an end-to-end manner. Exemplary control planes mayinclude Automatically Switched Optical Network (ASON) as defined inITU-T G.8080/Y.1304, Architecture for the automatically switched opticalnetwork (ASON) (02/2005), the contents of which are herein incorporatedby reference; Generalized Multi-Protocol Label Switching (GMPLS)Architecture as defined in IETF Request for Comments (RFC): 3945(10/2004) and the like, the contents of which are herein incorporated byreference; Optical Signaling and Routing Protocol (OSRP) from CienaCorporation which is an optical signaling and routing protocol similarto PNNI (Private Network-to-Network Interface) and MPLS; or any othertype control plane for controlling network elements at multiple layers,and establishing connections therebetween. Control planes are configuredto establish end-to-end signaled connections to route the connectionsand program the underlying hardware accordingly. SDN provides themanagement of network services through abstraction of lower-levelfunctionality. This is done by decoupling the system that makesdecisions about where traffic is sent (the control plane) from theunderlying systems that forward traffic to the selected destination (thedata plane).

In control planes, SDN, and the like, network updates are floodedcontinually so that each node (in control planes) or an SDN controller(in SDN) have synchronized views of the network. As networks scale, theamount of updates can be difficult to process. For example, the updatescan be flooded through Protocol Data Unit (PDU) packets or the like,with different types of routing PDUs for different types of updates. Anexemplary routing PDU is a Link Bandwidth Update PDU to convey bandwidthupdates on a link, which is typically the most frequently floodedrouting PDU. Conventionally, many techniques are employed to reduce theeffects of flooding PDUs in the network, including the Link BandwidthUpdate PDUs. One exemplary technique includes setting bandwidththresholds for when Link Bandwidth Updates are flooded, i.e. when thebandwidth threshold is crossed then Link Bandwidth Update PDUs areflooded. This is described, for example, in commonly assigned U.S. Pat.No. 7,729,253 issued on Jun. 1, 2010 and entitled “REDUCED AVAILABLEBANDWIDTH UPDATES,” the contents of which are incorporated by referenceherein. Another exemplary technique involves constraining links overwhich all Routing PDUs are flooded, i.e., manually creating SpanningTree like paths to reach all nodes. This is described, for example, incommonly assigned U.S. Pat. No. 8,089,866 issued on Jan. 3, 2012 andentitled “SPANNING TREE FLOODING BACKBONE SYSTEMS AND METHODS FOR LINKSTATE ROUTED NETWORKS,” the contents of which are incorporated byreference herein. Yet another technique is to ensure only a singleRouting PDU of a given type (e.g., Link Bandwidth Update) is originatedwithin a given period of time, e.g. 2s.

As networks continue to scale, more effective techniques are required toimprove scalability, efficiency, and performance of routing updates andthe network in general.

BRIEF SUMMARY OF THE DISCLOSURE

In an exemplary embodiment, a method for reduced link bandwidth updatesfrom a first node and a second node forming a link in a networkincludes, responsive to establishment or release of one or moreconnections on the link, flooding an update related thereto from only amaster node that is one of the first node and the second node; and,responsive to an event besides the establishment or release of the oneor more connections on the link, flooding an update related thereto fromboth the first node and the second node. The flooding can be performedin a control plane associated with the network and/or to a SoftwareDefined Networking (SDN) controller. The control plane can be one ofAutomatically Switched Optical Network (ASON), GeneralizedMulti-Protocol Label Switching (GMPLS), and Optical Signaling andRouting Protocol (OSRP). The event can be a link failure or recoveryassociated with the link or a change in parameters associated with thelink. The flooding can be used to update a topology database associatedwith the network, and wherein only bandwidth on the link for the masternode is inspected for path computation. The topology database isup-to-date with respect to bandwidth on the link from a perspective ofthe master node and delayed with respect to a slave node. The masternode can be selected between the first node and the second node based onpredetermined criteria. The one or more connections are managedbi-directionally such that bandwidth for the one or more connections onthe link from the first node to the second node is equal to bandwidthfor the one or more connections on the link from the second node to thefirst node.

In another exemplary embodiment, a node, in a network, configured forreduced link bandwidth updates, includes one or more ports each formingan associated link in the network; and a controller configured to:responsive to establishment or release of one or more connections on thelink, flood an update related thereto only if the node is a master nodefor the link; and, responsive to an event besides the establishment orrelease of the one or more connections on the link, flood an updaterelated thereto regardless of whether or not the node is a master node.The controller can operate a control plane associated with the networkand/or communicates to a Software Defined Networking (SDN) controller.The control plane can be one of Automatically Switched Optical Network(ASON), Generalized Multi-Protocol Label Switching (GMPLS), and OpticalSignaling and Routing Protocol (OSRP). The event can be a link failureor recovery associated with the link or a change in parametersassociated with the link. The controller can be configured to: maintaina topology database associated with the network based on updatesreceived from other nodes; and, for path computation, inspect onlybandwidth for a master node on a particular link. The topology databasecan be up-to-date with respect to bandwidth on the link from aperspective of the master node and delayed with respect to a slave node.The master node can be determined based on predetermined criteria. Theone or more connections can be managed bi-directionally such thatbandwidth for the one or more connections on the link from the firstnode to the second node is equal to bandwidth for the one or moreconnections on the link from the second node to the first node.

In a further exemplary embodiment, a network with reduced link bandwidthupdates includes a plurality of nodes; a plurality of linksinterconnecting the plurality of nodes; wherein, for each of theplurality of links, associated nodes designate a master node, and, forbandwidth updates: responsive to establishment or release of one or moreconnections on a link, an update related thereto is flooded from only anassociated master node for the link; and, responsive to an event besidesthe establishment or release of the one or more connections on the link,an update related thereto is flooded from both nodes associated with thelink. A control plane can be operated in the network, and wherein thecontrol plane is one of Automatically Switched Optical Network (ASON),Generalized Multi-Protocol Label Switching (GMPLS), and OpticalSignaling and Routing Protocol (OSRP). The network can further include aSoftware Defined Networking (SDN) controller configured to receiveflooded updates from the plurality of nodes. Only bandwidth on the linkfor the master node is inspected for path computation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated and described herein withreference to the various drawings, in which like reference numbers areused to denote like system components/method steps, as appropriate, andin which:

FIG. 1 is a network diagram of an exemplary network with fiveinterconnected nodes;

FIG. 2 is a block diagram of an exemplary network element for use withthe systems and methods described herein;

FIG. 3 is a block diagram of a controller to provide control planeprocessing and/or operations, administration, maintenance, andprovisioning (OAM&P) for the network element of FIG. 2; and

FIG. 4 is a flow chart of a reduced link bandwidth update method.

DETAILED DESCRIPTION OF THE DISCLOSURE

In various exemplary embodiments, reduced link bandwidth update systemsand methods in control planes, SDN, and the like are described toimprove scalability, efficiency, and performance of routing updates andthe network in general. The reduced link bandwidth update systems andmethods propose to half the number of Link Bandwidth Updatenotifications by constraining the update to only one node on a link,i.e. a link in a network is formed between two nodes. Halving the numberof Link Bandwidth Update PDUs that are flooded in the network halves theamount of processing required by each node in the network to processsuch PDUs. Furthermore, such halved processing requirements are mostbeneficial when connections are mesh restoring in the network due tofailures, i.e. as failures occur, affected connections need to bereleased and re-established around the points of failure. As failedconnections are released and re-established on links, the amount ofavailable bandwidth changes on the links resulting in Link BandwidthUpdate PDUs getting generated for these links. Thus, any processinggains obtained from halving the number of Link Bandwidth Update PDUsmeans more processing is available to expedite the release andre-establishment of the failed connections, i.e. mesh restorationperformance is improved. Still furthermore, by halving the number ofLink Bandwidth Update PDUs, network scalability is improved, as well asthe use of control bandwidth is made more efficient. The reduced linkbandwidth update systems and methods described herein are acomplementary mechanism to reduce the effects of flooding Routing PDUsin the network, and are not intended to replace the existing mechanisms,i.e. they can all work in unison to reduce the effects of floodingRouting PDUs in the network to keep each node up-to-date with respect tothe current network state.

Exemplary Network

Referring to FIG. 1, in an exemplary embodiment, a network diagramillustrates an exemplary network 100 with five interconnected nodes 110a, 110 b, 110 c, 110 d, 110 e. The nodes 110 are interconnected througha plurality of links 120. The nodes 110 communicate with one anotherover the links 120, such as through Wavelength Division Multiplexing(WDM), Optical Transport Network (OTN), Ethernet, Internet Protocol(IP), Multiprotocol Label Switching (MPLS), SONET/SDH, and the like. Thenodes 110 can be network elements which include a plurality of ingressand egress ports forming the links 120. An exemplary network element110A is illustrated in FIG. 2. The network 100 includes a connection 130with ingress/egress at the nodes 110 a, 110 c and intermediate nodes 110b, 110 e. The connection 130 can be a Sub-Network Connection (SNC), aLabel Switched Path (LSP), an IP flow, or the like. The connection 130is an end-to-end signaled path and from the view of the client signalcontained therein, it is seen as a single network segment. Of course,the network 100 can include a plurality of connections. The nodes 110can also be referred to interchangeably as network elements (NEs). Thenetwork 100 is illustrated, for example, as an interconnected meshnetwork, and those of ordinary skill in the art will recognize thenetwork 100 can include other architectures, with additional nodes 110or with less nodes 110, etc.

The network 100 can include a control plane 140 operating on and/orbetween the nodes 110 a, 110 b, 110 c, 110 d, 110 e. The control plane140 includes software, processes, algorithms, etc. that controlconfigurable features of the network 100, such as automating discoveryof the nodes 110, capacity on the links 120, port availability on thenodes 110, connectivity between ports; dissemination of topology andbandwidth information between the nodes 110; calculation and creation ofpaths for connections; network level protection and restoration; and thelike. In an exemplary embodiment, the control plane 140 can utilizeASON, GMPLS, OSRP, MPLS, Open Shortest Path First (OSPF), IntermediateSystem-Intermediate System (IS-IS), or the like. Those of ordinary skillin the art will recognize the network 100 and the control plane 140 canutilize any type of control plane for controlling the nodes 110 andestablishing and maintaining connections therebetween, such as at andbetween Layers 0, 1, 2, 3+, etc. Layers 3+ include the network throughapplication layers (Layers 3-7).

An SDN controller 150 can also be communicatively coupled to the network100 through one or more of the nodes 110. SDN is an emerging frameworkwhich includes a centralized control plane decoupled from the dataplane. SDN works with the SDN controller 150 knowing a full networktopology through configuration or through the use of a controller-baseddiscovery process in the network 100. The SDN controller 150 differsfrom a management system in that it controls the forwarding behavior ofthe nodes 110 only, and performs control in real time or near real time,reacting to changes in services requested, network traffic analysis andnetwork changes such as failure and degradation. Also, the SDNcontroller 150 provides a standard northbound interface to allowapplications to access network resource information and policy-limitedcontrol over network behavior or treatment of application traffic. TheSDN controller 150 sends commands to each of the nodes 110 to controlmatching of data flows received and actions to be taken, including anymanipulation of packet contents and forwarding to specified egressports. Examples of SDN include OpenFlow(www.opennetworking.org/sdn-resources/onf-specifications/openflow/),General Switch Management Protocol (GSMP) defined in RFC 3294 (June2002), and Forwarding and Control Element Separation (ForCES) defined inRFC 5810 (March 2010), the contents of all are incorporated by referenceherein.

Exemplary Network Element/Node

Referring to FIG. 2, in an exemplary embodiment, a block diagramillustrates an exemplary network element 110A for use with the systemsand methods described herein. In an exemplary embodiment, the exemplarynetwork element 110A can be a network element that may consolidate thefunctionality of a Multi-Service Provisioning Platform (MSPP), DigitalCross Connect (DCS), Ethernet and/or Optical Transport Network (OTN)switch, Dense Wave Division Multiplexed (DWDM) platform, IP router, etc.into a single, high-capacity intelligent switching system providingLayer 0, 1, 2 and/or 3 consolidation. In another exemplary embodiment,the network element 110A can be any of an OTN Add/Drop Multiplexer(ADM), Reconfigurable Optical Add/Drop Multiplexer (ROADM), an MSPP, aDigital Cross-Connect (DCS), an optical cross-connect, an opticalswitch, a router, a switch, a DWDM platform, an access/aggregationdevice, etc. That is, the network element 110A can be anydigital/optical system with ingress and egress digital/optical signalsand switching therebetween of channels, timeslots, tributary units, etc.and/or photonic system with ingress and egress wavelengths and switchingtherebetween. While the network element 110A is generally shown as anoptical network element, the systems and methods are contemplated foruse with any network device including packet switches, bridges, routers,or the like.

In an exemplary embodiment, the network element 110A includes commonequipment 210, one or more line modules 220, and one or more switchmodules 230. The common equipment 210 can include power; a controlmodule; operations, administration, maintenance, and provisioning(OAM&P) access; user interface ports; and the like. The common equipment210 can connect to a management system 250 through a data communicationnetwork 260 (as well as a Path Computation Element (PCE), SoftwareDefined Network (SDN) controller, OpenFlow controller, etc.). Themanagement system 250 can include a network management system (NMS),element management system (EMS), or the like. Additionally, the commonequipment 210 can include a control plane and OAM&P processor, such as acontroller 300 illustrated in FIG. 3, configured to operate the controlplane, along with other functions as described herein. Through thecommon equipment 210, a user or network operator can gain OAM&P accessto the network element 110A, either remotely or locally. The remoteaccess can be via the DCN 260 and/or the management system 250, and thelocal access can be via a craft interface or management port associatedwith the network element 110A for switching functions, OAM functions,etc.

The network element 110A can include an interface 270 forcommunicatively coupling the common equipment 210, the line modules 220,and the switch modules 230 therebetween. For example, the interface 270can be a backplane, mid-plane, a bus, optical or electrical connectors,or the like. The line modules 220 are configured to provide ingress andegress to the switch modules 230 and to external connections on thelinks 120 to/from the network element 110A. In an exemplary embodiment,the line modules 220 can form ingress and egress switches with theswitch modules 230 as center stage switches for a three-stage switch,e.g. a three stage Clos switch. Other configurations and/orarchitectures are also contemplated. The line modules 220 can includeoptical transceivers, such as, for example, 1 Gb/s (GbE PHY), 2.5 GB/s(OC-48/STM-1, OTU1, ODU1), 10 Gb/s (OC-192/STM-64, OTU2, ODU2, 10 GbEPHY), 40 Gb/s (OC-768/STM-256, OTU3, ODU3, 40 GbE PHY), 100 Gb/s (OTU4,ODU4, 100 GbE PHY), ODUflex, OTUCn, etc. Functionally, the line modules220 form one or more ports for network access and various functionsassociated therewith. That is, the line modules 220 can form the links120 with their associated bandwidth.

Further, the line modules 220 can include a plurality of opticalconnections per module and each module may include a flexible ratesupport for any type of connection, such as, for example, 155 MB/s, 622MB/s, 1 GB/s, 2.5 GB/s, 10 GB/s, 40 GB/s, 100 GB/s, 200 GB/s, 400 GB/s,N×1.25 GB/s, and any rate in between. The line modules 220 can includewavelength division multiplexing interfaces, short reach interfaces, andthe like, and can connect to other line modules 220 on remote networkelements, end clients, edge routers, and the like. From a logicalperspective, the line modules 220 provide ingress and egress ports tothe network element 110A, and each line module 220 can include one ormore physical ports. The switch modules 230 are configured to forwardchannels, wavelengths, timeslots, tributary units, packets, etc. betweenthe line modules 220. For example, the switch modules 230 can providewavelength granularity (Layer 0 switching), SONET/SDH granularity suchas Synchronous Transport Signal-1 (STS-1) and variants/concatenationsthereof (STS-n/STS-nc), Synchronous Transport Module level 1 (STM-1) andvariants/concatenations thereof, Virtual Container 3 (VC3), etc.; OTNgranularity such as Optical Channel Data Unit-1 (ODU1), Optical ChannelData Unit-2 (ODU2), Optical Channel Data Unit-3 (ODU3), Optical ChannelData Unit-4 (ODU4), Optical Channel Data Unit-flex (ODUflex), Opticalchannel Payload Virtual Containers (OPVCs), ODTUGs, etc.; Ethernetgranularity; Digital Signal n (DSn) granularity such as DS0, DS1, DS3,etc.; and the like. Specifically, the switch modules 230 can includeTime Division Multiplexed (TDM) (i.e., circuit switching), packetswitching engines, and/or bridging or routing engines. The switchmodules 230 can include redundancy as well, such as 1:1, 1:N, etc. In anexemplary embodiment, the switch modules 230 can provide wavelengthswitching such as through a Wavelength Selective Switch (WSS) or thelike.

Those of ordinary skill in the art will recognize the network element110A can include other components which are omitted for illustrationpurposes, and that the systems and methods described herein iscontemplated for use with a plurality of different network elements withthe network element 110A presented as an exemplary type of a networkelement. For example, in another exemplary embodiment, the networkelement 110A may not include the switch modules 230, but rather have thecorresponding functionality in the line modules 220 (or some equivalent)in a distributed fashion. For the network element 110A, otherarchitectures providing ingress, egress, and switching therebetween arealso contemplated for the systems and methods described herein. Ingeneral, the systems and methods described herein contemplate use withany network element providing switching of channels, timeslots,tributary units, wavelengths, etc. with or without use of the controlplane 140 or the SDN controller 150. Furthermore, the network element110A is merely presented as one exemplary network element for thesystems and methods described herein.

Exemplary Controller

Referring to FIG. 3, in an exemplary embodiment, a block diagramillustrates a controller 300 to provide control plane processing and/oroperations, administration, maintenance, and provisioning (OAM&P) forthe network element 110A. The controller 300 can be part of commonequipment, such as common equipment 210 in the network element 110A, ora stand-alone device communicatively coupled to the network element 110Avia the DCN 260. The controller 300 can include a processor 310 which isa hardware device for executing software instructions such as operatingthe control plane. The processor 310 can be any custom made orcommercially available processor, a central processing unit (CPU), anauxiliary processor among several processors associated with thecontroller 300, a semiconductor-based microprocessor (in the form of amicrochip or chip set), or generally any device for executing softwareinstructions. When the controller 300 is in operation, the processor 310is configured to execute software stored within memory, to communicatedata to and from the memory, and to generally control operations of thecontroller 300 pursuant to the software instructions. The controller 300can also include a network interface 320, a data store 330, memory 340,an Input/output (I/O) interface 350, and the like, all of which arecommunicatively coupled therebetween and with the processor 310.

The network interface 320 can be used to enable the controller 300 tocommunicate on the DCN 260, such as to communicate control planeinformation to other controllers, SDN controllers, to the managementsystem 250, and the like. The network interface 320 can include, forexample, an Ethernet card (e.g., 10BaseT, Fast Ethernet, GigabitEthernet) or a wireless local area network (WLAN) card (e.g., 802.11).The network interface 320 can include address, control, and/or dataconnections to enable appropriate communications on the network. Thedata store 330 can be used to store data, such as control planeinformation, provisioning data, OAM&P data, etc. The data store 330 caninclude any of volatile memory elements (e.g., random access memory(RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memoryelements (e.g., ROM, hard drive, flash drive, CDROM, and the like), andcombinations thereof. Moreover, the data store 330 can incorporateelectronic, magnetic, optical, and/or other types of storage media. Thememory 340 can include any of volatile memory elements (e.g., randomaccess memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatilememory elements (e.g., ROM, hard drive, flash drive, CDROM, etc.), andcombinations thereof. Moreover, the memory 340 may incorporateelectronic, magnetic, optical, and/or other types of storage media. Notethat the memory 340 can have a distributed architecture, where variouscomponents are situated remotely from one another, but may be accessedby the processor 310. The I/O interface 350 includes components for thecontroller 300 to communicate with other devices. Further, the I/Ointerface 350 includes components for the controller 300 to communicatewith the other nodes, such as using overhead associated with OTNsignals. Also, the controller 300 can implement various routing andsignaling protocols to communicate with other nodes and controllers 300such as, for example, Border Gateway Protocol (BGP), Open Shortest PathFirst (OSPF), Intermediate System-Intermediate System (IS-IS), ResourceReservation Protocol-Traffic Engineering (RSVP-TE), and the like.

In an exemplary embodiment, the controller 300 is configured tocommunicate with other controllers 300 in the network 100 to operate thecontrol plane 140 and/or to communicate with the SDN controller. Thiscommunication may be either in-band or out-of-band. For SONET networksand similarly for SDH networks, the controllers 300 may use standard orextended SONET line (or section) overhead for in-band signaling, such asthe Data Communications Channels (DCC). Out-of-band signaling may use anoverlaid Internet Protocol (IP) network such as, for example, UserDatagram Protocol (UDP) over IP over the DCN 260. In an exemplaryembodiment, the controllers 300 can include an in-band signalingmechanism utilizing OTN overhead. The General Communication Channels(GCC) defined by ITU-T Recommendation G.709 are in-band side channelsused to carry transmission management and signaling information withinOptical Transport Network elements. The GCC channels include GCC0 andGCC1/2. GCC0 are two bytes within the Optical Channel Transport Unit-k(OTUk) overhead that are terminated at every 3R (Re-shaping, Re-timing,Re-amplification) point. GCC1/2 are four bytes (i.e. each of GCC1 andGCC2 include two bytes) within the Optical Channel Data Unit-k (ODUk)overhead. For example, GCC0, GCC1, GCC2 or GCC1+2 may be used forin-band signaling or routing to carry control plane traffic. Based onthe intermediate equipment's termination layer, different bytes may beused to carry control plane signaling. If the ODU layer has faults, ithas been ensured not to disrupt the GCC1 and GCC2 overhead bytes andthus achieving the proper delivery control plane signaling. Othermechanisms are also contemplated for control plane signaling.

Network Updates

Link State (LS) routing protocols such as OSPF, IS-IS, and PNNI requirean accurate view of the network topology (this includes knowledgeregarding the presence of the nodes 110 and the links 120, their networkaddress, and their state (up/down) as well as the value of all linkmetrics (e.g., their cost)) and bandwidth availability on such links inorder to calculate optimal routes to a destination node. These LSrouting protocols use topology-state update mechanisms to build atopology database at each node, typically conveying the topology statusthrough flooding (flooding is defined as the broadcasting of controlmessages containing link/node status and reachability informationthrough every link on every node in the network). OSPF uses link stateadvertisement (LSA), PNNI uses PNNI topology state elements (PTSE).Topology information in PNNI is distributed in PTSEs, which areencapsulated in PNNI topology state packets (PTSPs) and periodicallyflooded to other nodes in the domain through all available links. Aswith all LS protocols, both OSPF and PNNI use HELLO messages toestablish and maintain link adjacencies. Router/Switch nodes and linksgo up/down in the course of operation (due to fiber cuts,hardware/software failures, etc.); link state routing protocols employ aflooding mechanism to disseminate this “change of state” informationthroughout the autonomous system. Simply put, this means when a routergets a new LSA message, it sends that information out to all of itsdirectly connected networks. Or, if one of the links on a router changesstate or its cost, the router generates a new LSA, which isflooded/broadcast out to all of its ports.

In the network 100, the nodes 110 are configured to continually send outupdates, in an associated protocol, for the control plane 140, the SDNcontroller 150, and/or the management system 250. The associatedprotocol is based on the type of the control plane 140 (e.g., GMPLS,ASON, OSRP, etc.), the SDN controller 150, etc. These updates can be inthe form of PDUs based on the associated protocol. Those of ordinaryskill in the art recognize the various different types of updates thatare flooded such as nodal updates, link updates, link bandwidth updates,etc. For example, nodal updates can relate to a new node coming onlineor a configuration change at an existing node. Similarly, link updatescan relate to a new link coming online or a configuration change at anexisting link. As described herein, the link bandwidth updates provide anotification related to a bandwidth change on a link, and these aretypically the most frequently flooded updates as bandwidth on the linkchanges every time a connection on that link is established orterminated.

In various exemplary embodiments, the reduced link bandwidth updatesystems and methods half the number of link bandwidth updates throughassuming, for Layer 0 and Layer 1, that connections on links arebidirectional and utilize the same amount of bandwidth in receive andtransmit direction and thus bandwidth availability at the two ends of alink is identical. Here, with this assumption, only one node 110 needsto flood a link bandwidth update when bandwidth on the associated link120 changes. In Layer 0 (photonic) and Layer 1 (time divisionmultiplexed), it is a reasonable assumption that bandwidth availabilityon both ends is identical based on how networks are deployed andoperated. Assuming a link X is associated with nodes A, B, an updatestating Y bandwidth is available from node A to node B is equivalent toan update stating Y bandwidth is available from node B to node A. Inthis manner, only one of the nodes A, B needs to provide a linkbandwidth update.

Reduced Link Bandwidth Update Method

Referring to FIG. 4, in an exemplary embodiment, a flow chartillustrates a reduced link bandwidth update method 400. The reduced linkbandwidth update method 400 is operated on a specific link 120 at theassociated nodes 110 forming the specific link 120. The reduced linkbandwidth update method 400 operates responsive to a change associatedwith the link (step 405). The change can be anything such as a bandwidthchange due to a connection establishment or release, a link failure, alink update, etc. (step 410). As described herein, the connectionestablishment or release is where there is a normal addition or deletionof bandwidth on the link 120, such as through the control plane 140, theSDN controller 150, etc. Conventionally, when connections are beingestablished or released in the network 100, for a particular linktouched by a connection after being established or released on the link120, nodes 110 at both ends of the link flood a link bandwidth update(e.g., a Link Bandwidth Update PDU) to all other nodes 110 in thenetwork 100 to update bandwidth availability for the link 110 where suchavailability either includes or excludes the bandwidth of theconnection. For example, if an Optical channel Transport Unit-4 (OTU4)link between nodes X and Y presently has 25 available Optical channelData Unit-0 (ODU0) tributary slots and an ODU2 connection establishes onthat link, then bandwidth availability for that link changes to 17 ODU0sand thus both nodes X and Y flood a Link Bandwidth Update PDU containingthe new bandwidth availability of 17 ODU0s.

Again, the majority of networks only handle bidirectional connectionsand thus bandwidth availability on both ends of a link is always thesame and thus it would suffice if only one node flooded around a LinkBandwidth Update PDU to update topology databases on all the nodes 110in the network 100. Note, this assumption related to bidirectionalconnections is made due to the nature of Layer 0 and Layer 1 networks,but it can also extend to Layer 2, 3, etc. In the reduced link bandwidthupdate method 400, if the change (step 405) is related to theestablishment or release of one or more connections on the link 120(step 410), an update is flooded from one node 110 associated with thelink 120 only (step 415). The two nodes 110 associated with the link 120can determine who performs the flooding based on specific criteria, suchas node identifier (ID) (e.g., higher node ID is chosen to perform theflooding). Here, the selected node 110 to perform the flooding is themaster node and the other node 110 is the slave node. Note that masterand slave relationship is always with respect to a particular link. Thatis, it is possible that a node may be a master for one link and slavefor another link.

The reduced link bandwidth update method 400 halves the number of linkbandwidth updates that are flooded in the network 110 and thus wouldhalve the amount of CPU processing required by each node 110 (andassociated controller 300) in the network 110 or SDN controllerFurthermore, such halved CPU processing requirements would be of mostbenefit when connections are mesh restoring in the network 100 due tofailures, i.e. as failures occur, affected connections need to bereleased and re-established around the points of failure and thus anyCPU processing gains obtained from the reduced link bandwidth updatemethod 400 would mean more CPU processing is available to expedite therelease and re-establishment of the failed connections, i.e. meshrestoration performance is improved. Still furthermore, by halving thenumber of link bandwidth updates, network scalability is improved, aswell as the use of control bandwidth is made more efficient.

Note, the optimization in the step 415 is only applied to link bandwidthupdates related to connection establishments and releases, and is notintended to be used for link failures and updates to any TE attributesof the link. That is, when a link fails (step 410), then both end nodes110 flood an indication the link 120 is failed (step 420). Furthermore,when Traffic Engineering (TE) attributes, such as Admin Weight, Latency,or Shared Risk Link Group (SRLG) change, then again each end floods thenew values independently as these values may be changed/set on eitherend of the link (step 420). That is, when an event occurs besides theconnection establishments and releases, updates are flooded from eachnode associated with the link (step 420). Again, it is worth noting thatLink Bandwidth Update PDUs are the most frequently flooded PDUs in thenetwork 100.

Thus, for each link 120, there will be a master node and a slave node.The determination of such can be network wide based on predeterminedcriteria. It is unique to select one node at either side of a link to bea master node, and for such node being responsible for flooding LinkBandwidth Update PDUs when bandwidth availability changes on the link,while the other node only floods Link Bandwidth Update PDUs at regularintervals or whenever the link fails or its TE parameters change, pernormal behavior. Furthermore, path computation only inspects bandwidthavailability at the side of the link flooded by the master node. Bothnodes will originate updates that are flooded, but the slave node willdo so less frequently than the master node. That is, the master nodewill always flood link bandwidth updates whereas the slave node willnot. One advantage of the reduced link bandwidth update method 400 isthat it does not require modification to the existing Link StateProtocols. The nodes 110 operate per normal behavior with the slave nodeconstraining flooding associated with link bandwidth updates.

At each node 110 and/or the SDN controller 150, the link bandwidthupdates are received and used to update a topology database of thenetwork 100. The reduced link bandwidth update method 400 contemplatesstandard operation of the topology database as per existing behavior.With the reduced link bandwidth update method 400, the topology databasewill only be out of synch with respect to bandwidth on the link 120 atthe slave node. Thus, for path computation, existing behavior requiresmodification. The path computation, when determining whether aparticular link 120 has sufficient bandwidth for a new connection, onlythe master node side of the link 120 needs to be examined for bandwidthavailability as it would have the most up to date values, based on thereduced flooding. Conventionally, bandwidth availability for both sidesof a link is examined. Thus, the reduced link bandwidth update method400 also improves path computation performance.

It will be appreciated that some exemplary embodiments described hereinmay include one or more generic or specialized processors (“one or moreprocessors”) such as microprocessors, digital signal processors,customized processors, and field programmable gate arrays (FPGAs) andunique stored program instructions (including both software andfirmware) that control the one or more processors to implement, inconjunction with certain non-processor circuits, some, most, or all ofthe functions of the methods and/or systems described herein.Alternatively, some or all functions may be implemented by a statemachine that has no stored program instructions, or in one or moreapplication specific integrated circuits (ASICs), in which each functionor some combinations of certain of the functions are implemented ascustom logic. Of course, a combination of the aforementioned approachesmay be used. Moreover, some exemplary embodiments may be implemented asa non-transitory computer-readable storage medium having computerreadable code stored thereon for programming a computer, server,appliance, device, etc. each of which may include a processor to performmethods as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, an optical storage device, a magnetic storage device, a ROM(Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM(Erasable Programmable Read Only Memory), an EEPROM (ElectricallyErasable Programmable Read Only Memory), Flash memory, and the like.When stored in the non-transitory computer readable medium, software caninclude instructions executable by a processor that, in response to suchexecution, cause a processor or any other circuitry to perform a set ofoperations, steps, methods, processes, algorithms, etc.

Although the present disclosure has been illustrated and describedherein with reference to preferred embodiments and specific examplesthereof, it will be readily apparent to those of ordinary skill in theart that other embodiments and examples may perform similar functionsand/or achieve like results. All such equivalent embodiments andexamples are within the spirit and scope of the present disclosure, arecontemplated thereby, and are intended to be covered by the followingclaims.

What is claimed is:
 1. A method for reduced link bandwidth updates froma first node and a second node forming ends of a link in a network, themethod comprising: responsive and subsequent to establishment or releaseof one or more connections on the link at the first node and the secondnode, flooding an update related thereto to all other nodes in thenetwork from only a master node that is one of the first node and thesecond node, wherein the master node is selected between the first nodeand the second node based on a unique network identifier of each nodewhich is known networkwide and designation of the master node is basedon the link such that a node could be both a master node and a slavenode for different links; and responsive to an event other than theestablishment or release of the one or more connections on the link,flooding the update related thereto from both the first node and thesecond node, wherein the one or more connections operate at one or bothof Layer 0 and Layer 1 and the flooded update includes bandwidthavailable at the one or both of Layer 0 and Layer
 1. 2. The method ofclaim 1, wherein the flooding is performed in a control plane associatedwith the network and/or to a Software Defined Networking (SDN)controller.
 3. The method of claim 2, wherein the control plane is oneof Automatically Switched Optical Network (ASON), GeneralizedMulti-Protocol Label Switching (GMPLS), and Optical Signaling andRouting Protocol (OSRP).
 4. The method of claim 1, wherein the event isa link failure or recovery associated with the link or a change inparameters associated with the link.
 5. The method of claim 1, whereinthe flooding is used to update a topology database associated with thenetwork, and wherein only bandwidth on the link for the master node isinspected for path computation.
 6. The method of claim 5, wherein thetopology database is up-to-date with respect to bandwidth on the linkfrom a perspective of the master node and delayed with respect to aslave node.
 7. The method of claim 1, wherein the one or moreconnections are managed bi-directionally such that bandwidth for the oneor more connections on the link from the first node to the second nodeis equal to bandwidth for the one or more connections on the link fromthe second node to the first node.
 8. A node, in a network, configuredfor reduced link bandwidth updates, the node comprising: one or moreports each forming an associated link in the network; and a controllerconfigured to: responsive and subsequent to establishment or release ofone or more connections on the link at a first node and a second node,flood an update related thereto to all other nodes in the network onlyif the node is a master node for the link, wherein the master node isdetermined based on a unique network identifier of each node which isknown networkwide and designation of the master node is based on thelink such that a node could be both a master node and a slave node fordifferent links; and responsive to an event other than the establishmentor release of the one or more connections on the link, flood the updaterelated thereto regardless of whether or not the node is a master node,wherein the one or more connections operate at one or both of Layer 0and Layer 1 and the flooded update includes bandwidth available at theone or both of Layer 0 and Layer
 1. 9. The node of claim 8, wherein thecontroller operates a control plane associated with the network and/orcommunicates to a Software Defined Networking (SDN) controller.
 10. Thenode of claim 9, wherein the control plane is one of AutomaticallySwitched Optical Network (ASON), Generalized Multi-Protocol LabelSwitching (GMPLS), and Optical Signaling and Routing Protocol (OSRP).11. The node of claim 8, wherein the event is a link failure or recoveryassociated with the link or a change in parameters associated with thelink.
 12. The node of claim 8, wherein the controller configured to:maintain a topology database associated with the network based onupdates received from other nodes; and for path computation, inspectonly bandwidth for a master node on a particular link.
 13. The node ofclaim 12, wherein the topology database is up-to-date with respect tobandwidth on the link from a perspective of the master node and delayedwith respect to a slave node.
 14. The node of claim 8, wherein the oneor more connections are managed bi-directionally such that bandwidth forthe one or more connections on the link from the first node to thesecond node is equal to bandwidth for the one or more connections on thelink from the second node to the first node.
 15. A network with reducedlink bandwidth updates, the network comprising: a plurality of nodes;and a plurality of links interconnecting the plurality of nodes;wherein, for each of the plurality of links, associated nodes designatea master node, and, for bandwidth updates: responsive and subsequent toestablishment or release of one or more connections on a link at a firstnode and a second node, an update related thereto is flooded to allother nodes in the network from only an associated master node for thelink, wherein the associated master node is determined based on a uniquenetwork identifier of each node which is known networkwide anddesignation of the master node is based on the link such that a nodecould be both a master node and a slave node for different links; andresponsive to an event other than the establishment or release of theone or more connections on the link, the update related thereto isflooded from both nodes associated with the link, wherein the one ormore connections operate at one or both of Layer 0 and Layer 1 and theflooded update includes bandwidth available at the one or both of Layer0 and Layer
 1. 16. The network of claim 15, wherein a control plane isoperated in the network, and wherein the control plane is one ofAutomatically Switched Optical Network (ASON), GeneralizedMulti-Protocol Label Switching (GMPLS), and Optical Signaling andRouting Protocol (OSRP).
 17. The network of claim 15, further comprisinga Software Defined Networking (SDN) controller configured to receiveflooded updates from the plurality of nodes.
 18. The network of claim15, wherein only bandwidth on the link for the master node is inspectedfor path computation.